Devices having or associated with a high level of security, such as gaming devices which have to meet stringent regulations, often utilize a secure boot chain so that there is a high level of certainty that the device has booted without being tampered with. One prior art technique is to provide a separate device on the board of the device to monitor an early part of the boot sequence to check that the boot loader (or BIOS) has not been tampered with. Further elements in the boot chain then build on the corner stone of the initial part of the boot sequence being secure to conduct further security checks. A problem with this technique is that if there is a need to update the boot loader, it is also necessary to update the monitoring device. There is a need for an alternative security method.